<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>

<body>

    <div id="app">
        <cpn></cpn>
        <cpn ref="aaa"></cpn>
        <button @click="fartherClick">父组件按钮</button>
    </div>

    <template id="cpn">
        <div style="border:1px solid green">
            <h2>我是cpn组件</h2>
            <ccpn></ccpn>
        </div>
    </template>

    <template id="ccpn">
        <div>
            <h2>我是子组件</h2>
            <button @click="btnClick">按钮</button>
        </div>
    </template>

    <script src="https://cdn.bootcdn.net/ajax/libs/vue/2.6.0/vue.js"></script>
    <script>
        const app = new Vue({
            el: '#app',
            data: {
                message: 'root . message'
            },
            methods: {
                fartherClick() {
                    // 1.$children
                    console.log(this.$children);
                    // for (let c of this.$children) {
                    //   console.log(c.name);
                    //   c.showMessage();
                    // }
                    // console.log(this.$children[3].name);

                    // 2.$refs => 对象类型, 默认是一个空的对象 ref='bbb'
                    console.log(this.$refs.aaa.name);
                },
            },
            components: {
                cpn: {
                    template: '#cpn',
                    data() {
                        return {
                            name: '我是cpn组件的name'
                        }
                    },
                    components: {
                        ccpn: {
                            template: '#ccpn',
                            methods: {
                                btnClick() {
                                    // 1.访问父组件$parent
                                    console.log(this.$parent);
                                    console.log(this.$parent.name);

                                    // 2.访问根组件$root
                                    console.log(this.$root);
                                    console.log(this.$root.message);
                                }
                            }
                        }
                    }
                }
            }
        })
    </script>

</body>

</html>